Cutting device of packaging machine

ABSTRACT

A cutting device is incorporated in a packaging machine having at least one expansion cylinder consisting of upper and lower sections with a gap therebetween. The cutting device includes two rails located on opposite sides of the expansion cylinder and substantially parallel to each other. Two slide blocks are respectively and movably mounted on the rails for movement along the rails between first and second positions on opposite sides of the expansion cylinder. A single cutting blade is arranged between and carried by the slide blocks whereby when the slide blocks are moved along the rails between the first and second positions, the blade is driven to reciprocally pass through the gap between the upper and lower sections of the expansion cylinder. A driving device mechanically coupled to at least one of the slide blocks drives the slide blocks and the cutting blade to move linearly along the corresponding rails between the first and second positions and thus causing the cutting blade to reciprocally pass through the gap for cutting off a packaging material supplied to the expansion cylinder.

FIELD OF THE INVENTION

[0001] The present invention generally relates to a packaging machine for packaging an article with a tubular film, and in particular to a cutting device adapted in the packaging machine for cutting off a continuous length of the packaging material.

BACKGROUND OF THE INVENTION

[0002] Shrinkable films made of synthetic materials have been widely used to package consumer products, such as compact disk (CD) pack. The package operation is usually done with a packaging machine. FIG. 8 of the attached drawings shows an example of a conventional packaging machine. In the conventional packaging machine, a packaging material C in a continuous, flattened tubular configuration is supplied from a roll to a feeding mechanism A. The feeding mechanism A comprises a number of expansion cylinders B which expands the tubular packaging material C and fit the expanded tube over articles E to be packaged.

[0003] As shown in FIG. 9, a cutting device D is provided in the feeding mechanism A for cutting off the continuous packaging material C to desired lengths. The conventional cutting device D comprises a number of cutting blades D1 arranged around one expansion cylinder C (not shown in FIG. 9). Such an arrangement has certain disadvantages. For example, it has a complicated mechanical structure for it needs a number of cutting blades D1 driven by a complicated belt-pulley system D2. Such a complicated structure not only increases the overall manufacturing costs but also adding unnecessary expense and shutdown time for maintenance. In addition, arranging all the blades D1 exactly in a common plane is in general very difficult. Zigzag edges may thus be formed on the packaging material C by the blades D1 that are not perfectly aligned. Moreover, the cutting efficiency is low due to such a multiple blade arrangement.

[0004] Meanwhile, additional control measures or devices D4, D5, D6 have to be employed to cooperate with a driving device D3 for precisely controlling the operation of the cutting blades D1. Costs are thus further increased. Furthermore, the large number of cutting blades D1 may cause substantial noise during operations. In addition, the movement of the cutting blades D1 approaching and away from the packaging material C is also a cause of noise, especially when the approaching and leaving speed of the cutting blades D1 are not well controlled.

[0005] Further, such a complicated structure makes it very difficult to accommodate packaging materials of different sizes for one has to replace the original transmission system with a new one. Costs and shutdown time can be substantially increased.

[0006] U.S. Pat. No. 5,791,220, entitled “Cutting Device of Packing Apparatus” and U.S. Pat. No. 5,531,858, entitled “Shrinkable Label Inserting Machine” disclose packaging machines having a structure similar to the above discussed techniques and of course share the above disadvantages.

[0007] It is thus desirable to provide a cutting device to be incorporated in a packaging machine for alleviating the above mentioned problems.

SUMMARY OF THE INVENTION

[0008] Accordingly, an object of the present invention is to provide a cutting device of a packaging machine having a simple structure and thus low costs.

[0009] Another object of the present invention is to provide a cutting device capable to form an even and neat edge in cutting off a continuous packaging material.

[0010] Another object of the present invention is to provide a cutting device having a single cutting blade whereby maintenance requirement is reduced.

[0011] Another object of the present invention is to provide a cutting device employing commonly used linear transmission systems for simplifying the overall structure and reducing the costs.

[0012] A further object of the present invention is to provide a cutting device capable of cutting a continuous packaging material with different cutting speeds for accommodating packaging operations of different speeds.

[0013] A further object of the present invention is to provide a cutting device having a cutting blade moved in a controlled manner whereby noise generated by the movement can be reduced.

[0014] Yet a further object of the present invention is to provide a cutting device capable to accommodate packaging materials of different sizes.

[0015] To achieve the above objects, in accordance with the present invention, there is provided a cutting device adapted to be incorporated in a packaging machine for cutting off a continuous supply of packaging material. The cutting device comprises two rails located on opposite sides of an expansion cylinder of the packaging machine and substantially parallel to each other. Two slide blocks are respectively and movably mounted on the rails for movement along the rails between first and second positions on opposite sides of the expansion cylinder. A single cutting blade is arranged between and carried by the slide blocks whereby when the slide blocks are moved along the rails between the first and second positions, the blade is driven to reciprocally pass through the gap between the upper and lower sections of the expansion cylinder. A driving device mechanically coupled to at least one of the slide blocks drives the slide blocks and the cutting blade to move linearly along the corresponding rails between the first and second positions and thus causing the cutting blade to reciprocally pass through the gap for cutting off a packaging material supplied to the expansion cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof, with reference to the attached drawings, in which:

[0017]FIG. 1 is a perspective view of a cutting device adapted in a packaging machine and constructed in accordance with a first embodiment the present invention;

[0018]FIG. 2 is a side elevational view of FIG. 1 showing a cutting blade moving in a forward direction;

[0019]FIG. 3 is similar to FIG. 2 but showing the cutting blade moving in a backward direction;

[0020]FIG. 4 is a plot showing the moving speed of the cutting blade of the cutting device of the present invention;

[0021]FIG. 5 is a perspective view showing a cutting device in accordance with a second embodiment of the present invention;

[0022]FIG. 6 is a perspective view showing a cutting device in accordance with a third embodiment of the present invention;

[0023]FIG. 7 is a side elevational view of FIG. 6;

[0024]FIG. 8 is a perspective view of a conventional packaging machine in which the cutting device of the present invention may be adapted to replace a conventional cutting device thereof; and

[0025]FIG. 9 is a perspective view showing a conventional cutting device adapted in the packaging machine illustrated in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] With reference to the drawings and in particular to FIG. 1, a cutting device constructed in accordance with a first embodiment of the present invention, generally designated with reference numeral 100, comprises a pair of rails 10 substantially parallel to each other and located on opposite sides of an expansion cylinder B of a packaging machine A (see FIG. 8). In the embodiment illustrated, the expansion cylinder B consists of an upper cylindrical section B1 and a lower cylindrical section B2 co-axially aligned with each other with a gap X formed between confronting ends of the upper and lower sections B1, B2. A plurality of driving rollers B3, B4 are arranged beside the upper and lower sections B1, B2 of the expansion cylinder B for driving a tubular like packaging material C (see FIG. 8) in a downward direction, as viewed in the drawing of FIG. 1.

[0027] The cutting device 100 comprises a slide block 20 movably mounted on each rail 10 for carrying and driving linear movement of a cutting blade 30 along the rails 10. The gap X between the upper and lower sections B1, B2 of the expansion cylinder B is large enough to allow the cutting blade 30 to pass therethrough. Thus, when the slide blocks 20 reciprocate along the rails 10 between forward limit position and rear limit position, the cutting blade 30 is driven to reciprocally pass through the gap X, cutting off the packing material C fit over the cylinder B. The cutting blade 30 can be of any desired shape, such as a rhombus having sharp apex end 31, as illustrated in the drawings, for facilitating the cutting operation.

[0028] A driving device 40 capable of linear movement is coupled to at least one of the slide blocks 20 for reciprocally driving the cutting blade 30. The driving device 40 can of any devices that are capable to provide linear movement. In the embodiment illustrated, the driving device 40 comprises a motor 41 with a disk 42 mounted to a spindle 411 of the motor 41 and a link arm 43 coupling between the disk 42 and one of the slide blocks 20. A joint 431, 432 is formed on each end of the link arm 43 for rotatably connecting the end of the link arms 43 to the slide block 20 and the disk 42. The connection between the joint 431 and the disk 42 comprises a rod 433 extending through a radially-extending slot 421 defined in the disk 42. The rod 433 is movable along the slot 421 and is selectively and releasably secured at any desired position along the slot 421 by any known means. For example, threading (not shown) can be formed on the rod 433 for engaging with a nut (not shown) to releasably secure the rod 433 to the disk 42. The slot 42 is formed so that the rod 433 and joint 431 are offset or eccentric with respect to the spindle 411 of the motor 41 whereby when the disk 42 is rotated by the motor 41, the link arm 43 causes the slide block 20 and thus the cutting blade 30 to move reciprocally along the rails 10.

[0029] At least two sensors or detectors 50 are positioned on rear and front sides of the rails 10 for detecting the cutting blade 30. The sensors 50 set front and rear limitations of the movement of the blade 30. In this respect, the motor 41 may be controlled so that the rotation of the motor 41 is limited to be smaller than 180 degrees. In other words, the rotation of the motor 41 is reversed within an angular displacement smaller than 180 degrees. Idle time of the blade 30 at the limit positions can be set as desired. Alternatively, the disk 42 and the link arm 43 can be dimensioned to make the stroke of the blade 31 exactly corresponding to the limits set by the sensors 50 so that each time the disk 42 makes a full turn, the blade 30 is moved forth and back one time.

[0030] The motor 41 of the driving device 40 can be replaced by for example a servo motor and a step motor. The control of the servo motor or step motor can be done by means of a microprocessor based electronic controller or the equivalents.

[0031]FIGS. 2 and 3 respectively show forward and backward operations of the cutting device 100 of the present invention, namely forward and backward movements of the cutting blade 31. In the embodiment illustrated, when the motor 41 of the driving device 40 rotates a predetermined angle, such as 180 degrees, in the clockwise direction (as viewed in the drawing of FIG. 2), indicated by the arrow of FIG. 2, the cutting blade 30 is moved in a linear path along the rails 10 in a forward direction through the gap X between the upper and lower cylindrical sections B1, B2 of the expansion cylinder B, cutting off the packaging material C fit on the expansion cylinder B. After a predetermined time interval, the operation of the motor 41 is reversed, namely rotating counterclockwise as shown in FIG. 3, the blade 30 is driven backward, passing through the gap X and thus cutting off the packaging material C again. The portion of the packaging material C that is cut off is then driven by the rollers B4 toward and surrounding an article E to be packaged as shown in FIG. 7.

[0032] The cutting operation in accordance with the present invention is performed by means of a single cutting blade 30 which is far simpler in structure than the known devices discussed previously. Costs of manufacturing and maintenance can thus be substantially reduced. In addition, the sharp apex ends 31 formed on front and rear sides of the rhombus cutting blade 30 significantly facilitates the cutting operation done by the blade 30. Each forward and rearward stroke of the movement of the cutting blade 30 cuts off the packaging material C once so that the operation efficiency of cutting the packaging material C is twice as fast as the conventional devices. Further, the stoke of the cutting blade 30 can be readily adjusted by changing the position of the joint 431 along the slot 421 of the disk 42. The adjustment of the stroke of the blade 30 allows the cutting device 100 to accommodate packaging materials C of different dimensions (width). In this respect, the positions of the sensors 50 may also need to be adjusted.

[0033]FIG. 4 shows a plot of the speed of the cutting blade 30 of the cutting device 100. In the drawing, abscissa indicates “time” and ordinate represents “speed” of the cutting blade 30. The plot is divided into three phases, namely “IN”, “MID” and “OUT”. In the IN phase, the cutting blade 30 is moved in a direction toward the expansion cylinder B and is gradually accelerated from zero velocity to a preset maximum speed. This is generally achieved by the eccentric arrangement of the joint 431 with respect to the disk 42. When the cutting blade 30 is approaching the gap X of the expansion cylinder B, the speed reaches the maximum value in the MID phase and a quick cutting-off operation is done. Similarly, in the OUT phase, the speed of the cutting blade 30 is gradually decelerated to zero speed. Such an operation allows the blade 30 to form a neat and even cutting edge of the packaging material C.

[0034]FIG. 5 shows a second embodiment of the cutting device in accordance with the present invention. To simplify the description, the cutting device of the second embodiment is also designated with reference numeral 100. In the second embodiment, the driving device 40 comprises power cylinders, such as hydraulic cylinders and pneumatic cylinders. Each power cylinder 40 has a rod 40A connected to each of the slide blocks 20 for driving the cutting blade 30 linearly along the rails 10.

[0035]FIGS. 6 and 7 show a third embodiment of the cutting device in accordance with the present invention, also designated with reference numeral 100. The cutting device 100 of the third embodiment comprises a driving device 40′ consisting of a motor 41′ having an output spindle 411′, a secondary spindle 42′ spaced from and parallel to the output spindle 411′ of the motor 41′, each having a pulley (not labeled) formed thereon and a belt 43′ coupled between the pulleys. An attachment 431′ is mounted to and movable with the belt 43′. The spindles 411′ and 42′ are located on opposite sides of the expansion cylinder B whereby when the belt 43′ is driven by the motor 41′ to reciprocate, the attachment 431′ can be moved toward and away from the expansion cylinder B. The attachment 431′ is suitably connected to one of the slide blocks 20 whereby when the motor 41′ is in operation, the cutting blade 30 carried by the slide blocks 20 is driven through the gap X between the upper and lower cylindrical sections B1, B2 of the expansion cylinder B for cutting off the packaging material C.

[0036] Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims. 

What is claimed is
 1. A cutting device adapted to be incorporated in a packaging machine having an expansion cylinder consisting of upper and lower sections with a gap therebetween, the cutting device comprising: two rails located on opposite sides of the expansion cylinder and substantially parallel to each other; a slide block movably mounted on each of the rails whereby the slide block is movable between first and second positions on opposite sides of the expansion cylinder; a cutting blade arranged between and carried by the slide blocks whereby when the slide blocks are moved along the rails between the first and second positions, the blade is driven to pass through the gap between the upper and lower sections of the expansion cylinder; and a driving device mechanically coupled to at least one of the slide blocks for driving the slide block to move in a linear path along the corresponding rail between the first and second positions and thus causing the cutting blade to reciprocally pass through the gap for cutting off a packaging material supplied to the expansion cylinder.
 2. The cutting device as claimed in claim 1 further comprising at least two sensors positioned on opposite sides of the expansion cylinder along the rails.
 3. The cutting device as claimed in claim 1, wherein the cutting blade has sharp front and rear ends.
 4. The cutting device as claimed in claim 1, wherein the driving device comprises a motor to which a link arm is coupled in an offset fashion whereby when the motor is actuated, the link arm is driven to move in an eccentric fashion.
 5. The cutting device as claimed in claim 4, wherein a disk is concentrically mounted to the motor, a radially-extending slot being defined in the disk, the link arm having a first end to which a rotation joint is formed, the rotation joint being coupled to the disk by a rod extending through and releasably secured to the slot of the disk, the rod being selectively movable along the disk to adjust the eccentricity of the rod with respect to the motor.
 6. The cutting device as claimed in claim 5, wherein the link arm has a second end to which a rotation joint is formed for rotatably coupling to the slide block.
 7. The cutting device as claimed in claim 1, wherein the driving device comprises at least a power cylinder coupled to at least one of the slide blocks.
 8. The cutting device as claimed in claim 7, wherein the power cylinder comprises a hydraulic cylinder.
 9. The cutting device as claimed in claim 7, wherein the power cylinder comprises a pneumatic cylinder.
 10. The cutting device as claimed in claim 1, wherein the driving device comprises a motor having a first spindle, a second spindle spaced from and substantially parallel to and first spindle and a belt coupling between the spindles, an attachment mounted to the belt to be movable therewith, the attachment being connected to one of the slide blocks for driving the slide block to move along the rails. 